It is known to investigate samples with spectroscopic electromagnetic radiation. It is also known to place a source and a detector of electromagnetic radiation adjacent to one another and use reflecting means to direct an electromagnetic beam. For instance, a Patent to He et al., U.S. Pat. No. 5,963,327 describes use of a total internally reflecting prism to direct an incident beam of electromagnetic radiation progressing in a horizontally oriented plane into a vertically oriented plane so that it interacts with a sample at an intended angle of incidence, and then, via a second total internally reflecting prism redirect the reflected beam into the original horizontally oriented plane and into the detector. Said 327 Patent system enables a more compact arrangement than more conventional geometry systems which position source and detector on laterally opposite sides of a sample. It is also noted that the 327 Patent system positions an aperture at the input to the detector.
Said 327 Patent system separates the incident and reflected beams by positioning the total internally reflecting prisms which intercept the incident and reflected beams, (with respect to the sample), at some distance apart from one another. And, it is noted that two such reflective means are necessary.
Also noted is a Patent to Johs, No. 5,929,993, which describes a total film retardance monitoring system and method of use, in which a monitored film is transferred between feed and take-up reels.
It would be of benefit if a single reflecting means could be utliized in a system which positions source and detector adjacent to one another, and if there was no necessity of changing the locus of the beam into an orthogonally related plane.
It is also known that when a beam of electromagnetic radiation is caused to impinge on the surface of a sample at an oblique or normal angle, reflected electromagnetic radiation from said sample generally contains components not only from its surface, but also from the backside thereof. The effect of said backside reflections can be difficult to model, and makes characterization of surface films far more difficult, even essentially impossible. It is therefore desirable to reduce of eliminate the presence of said backside reflections.